The immune system in humans and other mammals is a network of organs and cells that defend the body. This is how it works – when it detects foreign invaders like bacteria or viruses, it sends cells to attack and destroy them.

But not all immune systems work only that way, scientists at Stanford University have found. Their experiments showed that specialised gland cells of the flatworm do not slowly fight off a threat; they self-explode, taking down foreign cells around them, much like a cell grenade.

Chew Chai, a postdoctoral researcher at Stanford, was studying whether flatworms could tell their own tissue apart from tissue belonging to another worm. To test this, she cut flatworms lengthwise and fused them with tissue from another worm. 

While such worms can readily regenerate their own tissues, Chai found that they rejected tissue from unrelated worms, much like how a human body rejects a transplanted organ. 

“It’s this huge inflammatory response. Like there’s a fire and an alarm goes off, and the cells just blow up,” said Chai, who is the lead author of the paper Explosive cytotoxicity of ruptoblasts bridges hormone surveillance and immune defense which was published in the journal Cell 

Ruptoblasts as an immune response

The researchers named this process “ruptosis” and the cells carrying it out “ruptoblasts.” These immune cells burst open, release toxic substances that kill nearby cells, and then disappear within five minutes.

Some mammalian cells and bacteria too are capable of explosive cell deaths to destroy threats. But they take a long time doing it.

“Some mammalian cells and bacteria may also do an explosive sort of cell death, but the timescale is really long. They are exploding, but it’s more like pores that slowly leak things out over the course of several hours. Ruptosis happens within seconds to minutes,” Chai said.

Researchers tested ruptoblasts against E. coli bacteria, human kidney cells, and mouse blood cells. The cells successfully destroyed all three targets.

“It demonstrates there are lots of different immune mechanisms out there. All these animals live in an environment where there are lots of bacteria, lots of viruses, and we know so little about their immune mechanisms,” said co-author Bo Wang.

The researchers felt that studying less conventional species may help scientists uncover new ideas for tackling some of medicine’s most challenging problems.

(This article has been curated by Paramita Datta, who is an intern with The Indian Express.)